Biologically active fragments of IL-1β

ABSTRACT

The subject invention concerns a nucleic acid comprising a nucleotide sequence encoding human interleukin-1 (IL-1), and fragments thereof, and the polypeptides and peptides obtained. Specifically, the subject invention comprises the cloning of a cDNA synthesized by reverse transcription of poly(A)RNA isolated from adherent human monocytes stimulated with bacterial endotoxin. Human IL-1 is useful to induce the production of IL-2 by activated T-cells; it also acts on B-cells and NK-cells. The subject invention further concerns antibodies that are immunoreactive with human IL-1β proteins.

The subject invention was made with government support under a research project supported by the National Institutes of Health (NIH) in NIH Grant Nos. A115614, A117833, and CA04186. The government has certain rights in this invention.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No. 08/071,031, filed Jun. 1, 1993, now U.S. Pat. No. 5,681,933; which is a continuation of Ser. No. 07/880,476, filed May 6, 1992, now abandoned; which is a continuation of Ser. No. 07/557,279, filed Aug. 30, 1990, now abandoned; which is a division of Ser. No. 07/185,731, filed Apr. 25, 1988, now U.S. Pat. No. 5,510,462; which is a division of Serial No. 07/004,319, filed Jan. 8, 1987, now U.S. Pat. No. 4,766,069; which is a continuation of Ser. No. 06/611,669, filed May 18, 1984, now abandoned.

BACKGROUND OF THE INVENTION

It is well established that mononuclear phagocytes are required for antigen recognition and lymphocyte activation, and that they play a vital role in the immune response of the host to infectious, inflammatory, and malignant disease. Several aspects of immunological function and host response to infection and injury are attributable to various proteins and other mediators released from stimulated mononuclear phagocytes (Dinarello, 1984). These include leukocytic pyrogen (LP), a mediator of fever; leukocytic endogenous mediator (LEM), an inducer of several components of the acute phase response; lymphocyte activating factor (LAF), which augments both lymphocyte proliferation and lymphokine production; and mononuclear cell factor (MCF), which induces prostaglandin E₂ and collagenase synthesis in synovial cells. It has been demonstrated that LP and LAF activity co-purify and share common physical characteristics (Rosenwasser et al., 1979); Rosenwasser et al., 1981; Murphy et al., 1980). Similarly, there is evidence that LP and LEM are closely related, if not the same molecule (Kampschmidt, 1981), and furthermore that LAF and MCF seem to be identical (Mizel et al., 1979). The term interleukin-1 (IL-1) is now used to describe these varied biological activities, although it is presently unclear whether IL-1 represents a single substance or a family of related molecules. Prior to the subject invention, the art had no knowledge of the nucleotide sequence encoding human IL-1. Though the art was aware of general cloning procedures, there is no teaching or suggestion in the prior art which could be used to identify and clone the nucleotide sequence coding for human IL-1.

BRIEF SUMMARY OF THE INVENTION

The subject invention concerns a nucleic acid comprising a nucleotide sequence encoding human IL-1, and fragments thereof, and to the polypeptides and peptides obtained therefrom. Specifically, the subject invention comprises the cloning of a cDNA synthesized by reverse transcription of poly(A)RNA isolated from adherent human monocytes stimulated with bacterial endotoxin. Injection of hybrid-selected poly(A)RNA into Xenopus laevis oocytes directed the synthesis of biologically active LAF. The nucleotide sequence, as well as immunoprecipitation of poly(A)RNA-directed reticulocyte translation, suggests that human IL-1 is initially synthesized as a precursor peptide with a molecular weight of 30,747.

The subject invention further concerns antibodies that are immunoreactive with purified human IL-1β proteins. Both polyclonal and monoclonal antibodies can be produced by immunizing a suitable host, utilizing standard procedures, with an IL-1β polypeptide according to the subject invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic summary of the strategy used for the nucleotide sequence determination.

FIGS. 2a and 2b show the consensus nucleotide sequence of a human monocyte IL-1 cDNA and the predicted amino acid sequence of the protein in single letter code.

DETAILED DISCLOSURE OF THE INVENTION

Monocytes were separated from lymphocytes in human peripheral blood mononuclear cells by using adherence to glass surfaces. The adherent monolayers (80-90% monocytes, as judged by microscopic examination of phagocytized staphylococcal particles) were stimulated with endotoxin. Total cellular nucleic acid was extracted from the adherent cell population, purified by centrifugation through CsCl (Chirgwin et al., 1979), and enriched for poly(A)RNA by passage over oligo dT cellulose (Bantle et al., 1976).

Aliquots of poly(A)RNA were assayed for protein synthesis by in vitro translation using rabbit reticulocyte lysate containing ³⁵ S-methionine (Pelham et al., 1976). The translation products were immunoprecipitated using rabbit anti-human IL-1 antiserum (Dinarello et al., 1977a; Dinarello et al., 1977b) and staphylococcal protein A (Kessler, 1975; Ivarie et al., 1979). The immunoprecipitates were analyzed by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and autoradiography. The reticulocyte translation of stimulated monocyte-derived poly(A)RNA exhibits two intense immunoprecipitable bands, migrating with apparent molecular weights of 42,100 and 39,800, which are absent in the unstimulated poly(A)RNA preparation. A third, weaker band, migrating at 28,000 molecular weight also appears to be stimulation-specific. The measurement of the apparent molecular weights of these three proteins as determined by SDS-PAGE seems to be dependent upon the conditions of the electrophoresis. These proteins are represented as the following: 43K band, 42,600±1100; 35K band, 34,678±4800; 26K band, 25,520±3300.

Several poly(A)RNA preparations extracted from 12-hour endotoxin-stimulated monocytes were pooled and fractionated by sucrose gradient sedimentation. Each fraction was precipitated with ethanol, translated in a reticulocyte lysate, and analyzed by immunoprecipitation and electrophoresis as described above. RNA from selected fractions was also injected into oocytes. The culture medium from each batch of 20 oocytes was passed over SEPHACRYL S-200, and the eluted fractions were assayed for LAF activity as described above. It is clear that the majority of the activity clusters around the fractions containing the 35K band (centering on fraction 13).

A cDNA library was prepared from endotoxin-stimulated monocyte poly(A)RNA using the technique and vector descnbed by Okayama and Berg (1982). This library was screened with ³² P-labelled cDNA probes prepared from stimulated and unstimulated monocyte poly(A)RNA as well as from RNA contained within fraction 12 of the sucrose gradient described above. As a result, five cDNA clones representing three different size-classes were isolated on the basis that they were stimulation-specific and strongly related to material contained within fraction 12 of the sucrose gradient.

The cDNAs were used to produce hybrid-selected RNA (Maniatis et al., 1982), which was analyzed by in vitro translation similar to that described above. cDNA from several clones hybridized to RNA which can be translated into a protein similar to that seen as a result of the translation of fraction 12 in the sucrose gradient profile.

Clone pA-26 possessed the highest efficiency for hybrid-selection of the target RNA and similarly was associated with the strongest hybridization affinity for the cDNA probes that were used for screening. The cDNA transcript contained in pA-26 was sequenced as shown in FIG. 1, and found to be approximately 920 base pairs in length. The single longest open reading frame for this sequence encoded a protein of approximately 6,800 molecular weight. Since this did not correspond to the molecular size expected on the basis of the protein found in the reticulocyte translation, it was concluded that the cDNA transcript was not full length. Moreover, when nick-translated pA-26 plasmid was hybridized to a Northern blot (Rave et al., 1979; Maniatis et al., 1982) of stimulated-monocyte poly(A)RNA, its complementary RNA appeared as a single band approximately 1600 nucleotides in length. Two additional cDNA libraries were constructed from 4-hour and 12-hour endotoxin-stimulated human monocyte poly(A)RNA using the newer Okayama and Berg (1983) procedure. The result was that five 4-hour and four 12-hour clones hybridized to a DNA probe synthesized from clone pA-26. The cDNA inserts of these clones were of three different size classes. The largest insert (1560 base pairs [bp], as determined by agarose gel electrophoresis) was contained in both 12-hour (one clone) and 4-hour (four clones) libraries.

The 4-hour clone pcD-415 hybridizes to an RNA preparation which has IL-1-like (LAF) biological activity when injected into Xenopus laevis oocytes. Furthermore, this activity is absent from unstimulated monocyte poly(A)RNA and from hybrid-selected RNA made from the control cDNA 12-hour clone pcD-1214, which is structurally unrelated to the pcD-415 clone. The elution position of this material on the SEPHACRYL S-200 column represents an approximate molecular weight of 20,000. This is in agreement with the molecular size of IL-1 isolated from stimulated monocyte media (Rosenwasser et al., 1981).

From the above, we concluded that the three structurally-related clones pA-26, pcD-415, and pcD-1218 contain cDNA for human monocyte IL1. These clones were sequenced by the dideoxy chain termination technique following subcloning in various bacteriophage M13 cloning vectors. FIG. 1 shows a schematic summary of the strategy used for sequence determination. The top scale indicates the nucleotide positions relative to position 1 of the sequence as detailed in FIGS. 2a and 2b. The line immediately below the scale represents the extent of the sequence. The bold portion of the line delineates the predicted coding region for the IL-1precursor. Restriction sites utilized in the sequencing procedure are indicated (open circles=HaeIII and closed circles=AluI). The arrows beneath each cDNA clone indicate the direction and extent of gel sequences read from the M13 subclones (Messing et al., 1982) (mp8 and mp9) using the dideoxy terminator method (Sanger et al., 1977; Biggin et al., 1983).

The consensus nucleotide sequence of human monocyte IL-1 cDNA and the predicted amino acid sequence of the protein is shown in FIGS. 2a and 2b. The apparent coding region corresponds to a molecular weight of 30,747 and is similar in size to the protein translated in reticulocyte lysates, described previously. Nucleotides are numbered with position 1 corresponding to the first nucleotide following the G tails resulting from cloning with the Okayama-Berg system. The amino acid residues are indicated by one-letter symbols and the canonical eukaryotic translational initiation consensus sequence (Kozak, 1984a and 1984b) is underlined. Boxed nucleotides represent a potential glycosylation site (Rubenstein, 1982) and a potential polyadenylation signal (Proudfoot et al., 1976).

As disclosed above, our criteria for IL-1 identification are stringent, relying on data both from immunoprecipitation and biological assay of in vitro translation products. The polypeptide(s) in question must be stimulation specific, immunoprecipitable, and demonstrate biological activity. Significantly, using these same criteria, little or no activity was observed in association with poly(A)RNA isolated from monocytes which were not stimulated by endotoxin. The reticulocyte lysate translation of poly(A)RNA extracted from stimulated cells reveals a major stimulation-specific polypeptide with a molecular weight which is similar to that predicted by the cDNA sequence. This corresponds to one of the two molecular weight species of IL-1 activity previously found in the medium of human monocytes following stimulation, as well as IL-1 recovered from human synovial fluid. In the subject disclosure, biological activity from microinjected Xenopus oocytes and the activity found in stimulated monocyte media, co-elute from SEPHACRYL S-200 with an apparent molecular weight of 20,000, corresponding to the species reported by most investigators. This monocyte-derived protein can be isolated from endotoxinstimulated monocytes incubated with ³⁵ S-methionine in culture yielding a biologically-active, radiolabelled molecule which migrates as a 22,000 molecular weight species when analyzed on the same SDS-PAGE system disclosed herein.

The cDNA nucleotide sequence suggests that the initial translation product is larger than the protein usually associated with IL-1 activity. We suggest, therefore, that a proteoltic "cascade" processes IL-1 following synthesis and/or release from stimulated monocytes. Throughout this proteolysis, the molecule remains biologically active. Data derived from in vitro pulse-chase experiments support a precursor-product relationship between a large protein (approximately 31,000 molecular weight) and a series of smaller species which cross-react with our anti-serum. An arrow in FIGS. 2a and 2b located between Ala₈ and Ser₉ marks a potential signal sequence cleavage site somewhat similar to that predicted for interleulin-2 (Taniguchi et al., 1983). A second arrow located between Lys₂₁₀ and Met₂₁₁ locates a potential cleavage site much like that described by Kronenberg et al. (1979) for the cleavage of the pro-sequence from bovine proparathyroid hormone. These two potential cleavage sites delineate a putative peptide of 23,000 molecular weight, which is in reasonable agreement with the 15,000 to 20,000 size range reported by most investigators for the primary IL-1 activity.

Clone (plasmid) pcD-415, which contains the cDNA for human monocyte IL-1, was deposited in an E. Coli HB101 host in the permanent collection of the Northern Regional Research Laboratory, U.S. Department of Agriculture, Peoria, Ill., USA on Apr. 27, 1984. The culture was assigned the accession number NRRL B-15770 by the repository. This deposit became available to the public upon the grant of U.S. Pat. No. 4,766,069. The deposit is also available as required by foreign patent laws in countries wherein counterparts of the subject application, or its progeny, are filed. However, it should be understood that the availability of a deposit does not constitute a license to practice the subject invention in derogation of patent rights granted by governmental action.

Recombinant plasmid pcD415 can be isolated from its E. coli HB101 host by well-known procedures, e.g., using cleared lysate-isopycnic density gradient procedures, and the like.

Also, it is within the skill of those in the art to vary the conditions disclosed herein for cloning the nucleotide sequence encoding human IL-1.

The cloned human IL-1 gene can be used to detect related DNAs in the human genome by well-known probe techniques. Further, unlimited amounts of nucleic acid comprising a nucleotide sequence encoding human IL-1 can be made by the cloned human IL-1 gene of the subject invention. Still further, the IL-1 produced by the cloned gene of the subject invention can be used to induce the production of IL-2 by activating T-cells (IL-2 stimulates the T-cells to proliferate). As reported in Science 221:1362-1364, "[r]researchers from NAIAID and the Food and Drug Administration (FDA), using a test tube assay, have recently found that interleukin-2 improved the function of T-cells from six AIDS patients" (p. 1362).

In vitro, IL-1 activates neutrophils to degranulate and is also chemotactic. The most studied effects of IL1 are on lymphocytes. IL-1 acts on B-cells, T-cells, as disclosed above, and NK-cells. On B-cells, IL-1 acts in conjunction with other B-cell activators as an adjuvant. It boosts B-cell proliferation and immunoglobulin synthesis (Lipsky et al., 1983; Falkoff et al., 1983). On T-cells, IL-1 acts as a co-factor for T-cells to produce various lymphokines. IL-2 and leukocyte migration inhibitory factor have been studied as lymphokines which require a signal from IL-1 in the absence of monocytes or antigen presenting accessory cells (Mizel, 1982).

Another aspect of IL-1 is its inflammatory properties. IL-1 has been isolated from the synovial fluid of patients with various forms of arthritis (Wood et al., 1983), and its ability to increase collagenase and prostaglandin E₂ from synovial cells implicates IL-1 in the pathogenesis of several arthritides. In muscle tissue, IL-1 also induces prostaglandin E₂ but this leads to increased lysosomal protease activity and increases protein breakdown from muscle tissue (Baracos et al., 1983). In brain tissue, IL-1 also increases prostaglandin E, and this plays a key role in the development of the febrile response (Dinarello, in Lymphokines). More recent research involves IL-1 in the induction of sleep (Kreuger et al., in press) and in fibroblast proliferation and collagen synthesis (Schmidt et al., 1982).

Because of its central role as a mediator of host immunological and defense functions, detection of IL-1 in different disease states is likely to shed light on certain pathological processes, and levels of IL-1 may indicate the severity of certain disease states where this is masked by special drugs. There is evidence that IL-1 production is reduced in human subjects with certain cancers (Hofmann et al., 1983) and malnutrition (Keenan et al., 1982) and this has been supported by studies in animal models.

Use of IL-1 as an immunological reagent in humans or animals is likely because of its ability to stimulate T- and B-cells and increase immunoglobulin synthesis. In fact, IL-1 appears to be an excellent candidate for the body's endogenous adjuvant. Thus, it is possible to use IL-1 or parts of the IL-1 molecule in certain immunogens.

A further aspect of the claimed invention are antibodies that are raised by immunization of an animal with a purified IL-1β polypeptide. Both polyclonal and monoclonal antibodies can be produced using standard procedures well known to those skilled in the art using the recombinant IL-1β polypeptides of the subject invention as an immunogen (see, for example, Monoclonal Antibodies: Principles and Practice, 1983; Monoclonal Hybridoma Antibodies: Techniques and Applications, 1982; Selected Methods in Cellular Immunology, 1980; Immunological Methods Vol. II, 1981; Practical Immunology, and Kohler et al., 1975).

Following are examples which illustrate procedures, including the best mode, for practicing the invention. These examples should not be construed as limiting. All percentages are by weight and all solvent mixture proportions are by volume unless otherwise noted.

EXAMPLE 1 Preparation of Poly(A)RNA

Human mononuclear cells (4-6×10⁹) were isolated from Ficoll-Hypaque gradient separation of plateletphoresis byproducts. Cells were washed 4× in 0.9% NaCl at 600×g to remove platelets. Monocytes were plated into flat glass bottles in RPMI (Gibco) containing 1% (v/v) heat-inactivated human AB serum at a density of 1.25×10⁶ cells/cm² and allowed to adhere for 1.5 hours at 37° C. The bottles were then vigorously shaken and the non-adherent population drained and counted. The total number of adherent monocytes was determined by subtracting the non-adhering cells from the total cell count. Replacement (serum-free) RPMI contained 300 ng/ml E. coli endotoxin (Difco). After 12 hours at 37° C., the medium was drained and the adherent monolayer lysed by the addition of 6M guanidinium thiocyanate (Chirgwin et al., 1979). The lysate was frozen at -70° C. and thawed prior to layering onto CsCl cushions as previously descnbed (Chirgwin et al., 1979). Poly(A)RNA was recovered from the crude nucleic acid pellets by binding to oilgo(dT) cellulose twice (Bantle et al., 1976). Total RNA isolated from adherent monocytes ranged from 100-200 μg/10⁹ cells, of which poly(A)RNA consistently represented 5-7%. Preparation of poly(A)RNA from "unstimulated" mononuclear cells by the same procedure but without stimulation or adherence yielded about 500 μg of total RNA/10⁹ cells, of which only 1-2% bound to oligo(dT) cellulose under the conditions used here.

EXAMPLE 2 In Vitro Translation of Poly(A)RNA

Rabbit reticulocyte lysate was prepared, optimized, and treated with micrococcal nuclease as described in Pelham et al. (1976). Each translation contained 1 μg poly(A)RNA in the presence of 100 μCi ³⁵ S-methionine/ml. After incubation for 1 hour at 37° C., samples were immunoprecipitated according to the method of Kessler et al. (1975) with some modifications. During pre-clearing, 20 μl of normal rabbit serum (NRS) was added to each sample. This was followed by a 2-hour incubation at 4° C., after which 100 μl (i.e., 10% (w/v)) protein A (IgGsorb, The Enzyme Center, Boston, Mass.) was added. Samples were allowed to incubate an additional 1 hour at room temperature, and the IgGsorb was then pelleted by centrifugation in a clinical centrifuge for 10 minutes at maximum speed. Supernates were transferred to fresh tubes and incubated for 18 hours at 4° C. with 20 μl of rabbit anti-human EP/LAF polyclonal serum (Dinarello et al., 1977a). This antiserum was prepared by 20 monthly immunizations of 15 kD human EP/LAF obtained after gel filtration (Dinarello et al., 1973) and has anti-human EP/LAF but no anti-human IL-2 activity. Next, 100 μl IgGsorb was added to each tube, followed by incubation at room temperature for 1 hour. IgGsorb was pelleted as described above and the pellet washed by vigorous vortexing with 1 ml aliquots (3×) 0.5% (v/v) TRITON X-100. Antigens were then solubilized by the addition of 20 μl electrophoresis buffer containing 6% SDS (Laemli, 1970) and subsequent boiling for 5 minutes. Again, IgGsorb was removed by microfuging for 3 minutes, and the supernatant was then loaded onto a 17.5% polyacrylamide gel (15×17×0.15 cm) (see Laemnli, 1970) for electrophoresis at 35 mAmp for 5 hours. Gels were treated with fluor (EnHance, NEN), dried, and then exposed to photographic film (Kodak, XAR-5) for 24-72 hours prior to development.

EXAMPLE 3 Sucrose Gradient Fractionation of Stimulated Monocyte Poly(A)RNA

The sucrose gradient procedure is a modification of that descnbed by Bleakley et al. (1981). Poly(A)RNA (50 μg prepared from stimulated human monocytes) was dissolved in 475 μl of water, heated to 65° C. for 30 minutes, quench-cooled on ice, and adjusted to 50 mM Tris-HCl, pH 7.5; 0.1% lithium dodecyl sulfate; and 1 mM EDTA (TLE buffer). Samples were loaded into isoldnetic TLE-sucrose gradients (10-28%) and centrifuged in an SW41 rotor (Beckman) for 19 hours (4° C.) at 35 Krpm. A parallel gradient was run with E. coli rRNA as markers. Gradients were fractionated (ISCO Model D) and ethanol precipitated. The RNA pellets were washed 2× in 70% ethanol and then resuspended in 3 μl distilled water. Aliquots of each fraction were translated in rabbit reticulocyte lysate, immunoprecipitated, and processed for electrophoresis and autoradiography as described above. In addition, selected fractions were microinjected into Xenopus oocytes for assessment of biological activity also as described above. Stage V oocytes (Dumont, 1972) were manually defolliculated in BARTH-X medium (Ford et al., 1977) from the ovaries of adult Xenopus laevis (Nasco, WI) that had been stimulated with human chorionic gonadotropin (Sigma) 1-6 weeks beforehand. These oocytes were each microinjected with 50 nl of poly(A)RNA solution in sterile distilled water (usually at 1-2 mg/ml). Controls were injected with a similar volume of distilled water only. Microinjected oocytes were incubated individually in round-bottom microtiter wells containing 10 μl BARTH-X to which was added antibiotics (per ml of culture media: 100 U penicillin; 100 μg streptomycin; 70 μg gentamicin; 2.5 μg amphotericin B) for 40-45 hours at 20° C. The BARTH-X medium from batches of 20 oocytes was pooled and fractionated by gel filtration on a SEPHACRYL S-200 column (0.6×54 cm) equilibrated in RPMI containing 1% (v/v) heat-inactivated, fetal calf serum. Each fraction (about 1 ml) was placed in 3,500 m.w. cutoff dialysis tubing and concentrated five-fold by submerging in polyethylene glycol 8000 before assaying for LAF activity as reported in Rosenwasser et al. (1981).

EXAMPLE 4 Biological Activity of Hybrid-Selected RNA

Oocytes were processed as disclosed in Example 3, except that incubation was for 20 hours, and oocytes were incubated in microtiter plate wells at a density of 5 oocytes per well in 50 μl BARTH-X media. LAF activity was assayed using a modification of the procedure described by Rosenwasser et al. (1981), in which the mouse thymocyte cells were substituted with the D10 cell line described by Kaye et al. (1983).

EXAMPLE 5 cDNA Clones

Three separate cDNA libraries were used to isolate the three cDNA clones shown in FIG. 1. The first, represented by clone pA-26, was constructed from 12-hour endotoxin-stimulated monocyte message using the original Okayama-Berg cloning vector system (Okayama and Berg, 1982). The second and third libraries, represented by clones pcD-415 and pcD-1218, are from, respectively, 4-hour and 12-hour endotoxin-stimulated monocyte message using the newer Okayama-Berg cloning vector system (Okayama and Berg, 1983). Libraries were each created using 2 μg of S poly(A)RNA. A portion of the first library consisting of approximately 100 clones was screened with three different cDNA probes synthesized from stimulated and unstimulated monocyte poly(A)RNA as well as poly(A)RNA contained in fraction 12 of the sucrose gradient disclosed in Example 3. As a result, five clones appeared to be more closely related to the enriched cDNA probe than to the unstimulated RNA-derived probe. The two clones containing the longest nucleotide sequence appeared to be identical on the basis of restriction mapping. One clone, pA-26, was subcloned in M13mp11 following treatment with Bal31 exonuclease (Wei et al., 1983). The second and third cDNA libraries were screened with one of the M13 subclones of pA-26 cDNA using a hybridization probe primer (Hu et al., 1983).

The cDNA transcript can be obtained from the clones in essentially pure form by standard art methods. For example, the cDNA transcript in clone pcD415 can be clipped from the plasmid by a BamHI-PstI double-digestion (Okayama and Berg, 1983) and isolated by standard procedures. The essentially pure cDNA thus obtained can be used for subcloning into a different transfer vector.

As is well known in the art, the amino acid sequence of a protein, e.g. IL-1, is determined by the nucleotide sequence of the DNA. Because of the redundancy of the genetic code, i.e. more than one coding nucleotide triplet (codon) can be used for most of the amino acids used to make proteins, different nucleotide sequences can code for a particular amino acid. Thus the genetic code can be depicted as follows:

    ______________________________________                                         Phenylalanine (Phe)                                                                         TTK      Histidine (His)                                                                             CAK                                           Leucine (Leu) XTY Glutamine (Gln) CAJ                                          Isoleucine (Ile) ATM Asparagine (Asn) AAK                                      Methionine (Met) ATG Lysine (Lys) AAJ                                          Valine (Val) GTL Aspartic acid (Asp) GAK                                       Serine (Ser) QRS Glutamic acid (Glu) GAJ                                       Proline (Pro) CCL Cysteine (Cys) TGK                                           Threonine (Thr) ACL Tryptophan (Trp) TGG                                       Alanine (Ala) GCL Arginine (Arg) WGZ                                           Tyrosine (Tyr) TAK Glycine (Gly) GGL                                           Termination signal TAJ                                                         Termination signal TGA                                                       ______________________________________                                    

Key: Each 3-letter deoxynucleotide triplet corresponds to a trinucleotide of mRNA, having a 5'-end on the left and a 3'-end on the right. All DNA sequences given herein are those of the strand whose sequence correspond to the mRNA sequence, with thymine substituted for uracil. The letters stand for the purine or pyrimidine bases forming the deoxynucleotide sequence.

A=adenine

G=guanine

C=cytosine

T=thymine

X=T or C if Y is A or G

X=C if Y is C or T

Y=A, G, C or T if X is C

Y=A or G if X is T

W=C or A if Z is A or G

W=C if Z is C or T

Z=A, G, C or T if W is C

Z=A or G if W is A

QR=TC if S is A, G, C or T; alternatively

QR=AG if S is T or C

J=A or G

K=T or C

L=A, T, C or G

M=A, C or T

The above shows that the novel amino acid sequence of human IL-1 can be prepared by nucleotide sequences other than that in clone pcD-415. Functionally equivalent nucleotide sequences encoding the novel amino acid sequence of human IL-1, or fragments thereof having IL-1 activity, can be prepared by known synthetic procedures. Accordingly, the subject invention includes such functionally equivalent nucleotide sequences.

The one-letter symbol for the amino acids used in FIGS. 2a and 2b is well known in the art. For convenience, the relationship of the three-letter abbreviation and the one-letter symbol for amino acids is as follows:

    ______________________________________                                                      Ala  A                                                              Arg R                                                                          Asn N                                                                          Asp D                                                                          Cys C                                                                          Gln Q                                                                          Glu E                                                                          Gly G                                                                          His H                                                                          Ile I                                                                          Leu L                                                                          Lys K                                                                          Met M                                                                          Phe F                                                                          Pro P                                                                          Ser S                                                                          Thr T                                                                          Trp W                                                                          Tyr Y                                                                          Val V                                                                        ______________________________________                                    

Thus, the scope of the subject invention includes not only the specific nucleotide sequence depicted herein, but also all equivalent nucleotide sequences coding for molecules with human IL-1 biological activity. The term "equivalent" is being used in its ordinary patent usage here as denoting a nucleotide sequence which performs substantially as the nucleotide sequence identified herein to produce molecules with substantially the same human IL-1 biological activity in essentially the same kind of hosts. Within this definition are subfragments which have human IL-1 biological activity.

It is well within the skill of those in the genetic engineering art to use the nucleotide sequences encoding human IL-1 activity of the subject invention to produce human IL-1 via microbial processes. Fusing the sequences into an expression vector and transforming or transfecting into hosts, either eukaryotic (yeast or mammalian cells) or prokaryotic (bacterial cells), are standard procedures used in producing other well-known proteins, e.g., insulin, interferons, human growth hormone, and the like. Similar procedures, or obvious modifications thereof, can be employed to prepare human IL-1 proteins by microbial means or mammalian tissue-culture technology in accord with the subject invention.

As disclosed previously, the cDNA sequence in FIGS. 2a and 2b discloses, via two arrows, a cDNA sequence which itself encodes a peptide having human IL-1 activity. The isolation of this cDNA sequence is disclosed hereinafter. Upon isolation of this cDNA sequence in its essentially pure form, it can be cloned by using the procedures described herein for the entire cDNA sequence encoding human IL-1. Those skilled in the art will appreciate the fact that the cDNA fragment depicted includes substantially biologically (human IL-1 activity) equivalent cDNA sequences, as defined above.

The process for isolating the cDNA fragment is as follows: Plasmid pcD-415 is digested with StuI and XhoI restriction endonucleases in order to generate a DNA fragment containing approximately 1370 bp of sequence. The sequence of interest (between positions 111-717, FIGS. 2a and 2b) is approximately centered within this fragment (approximately 350 nucleotides from each end). These excess terminal nucleotides can be removed using a time-controlled Bal31 exonuclease limited digestion (Wei et al., 1983). In this way, a fragment containing the DNA sequence corresponding to that located between the two arrows in FIGS. 2a and 2b can be generated. Using a combination of techniques which are well known in the art the resulting Bal31 fragments can be subcloned and then selected using radioactive probes made from restriction endonuclease digestion fragments made from the original pcD-415 cDNA insert.

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We claim:
 1. A purified polypeptide fragment of a human IL-1β precursor polypeptide, wherein said fragment is a truncated fragment of said human IL-1β precursor polypeptide, with the proviso that said polypeptide fragment of human IL-1 β precursor polypeptide is not the mature form of human IL-1β, and wherein said polypeptide fragment of said human IL-1β precursor polypeptide has IL-1β biological activity as determined in a mouse thymocyte assay.
 2. The polypeptide fragment according to claim 1, wherein said human IL-1β precursor polypeptide has the amino acid sequence shown in FIGS. 2a and 2b.
 3. The polypeptide fragment according to claim 1, wherein said polypeptide fragment has a molecular weight of between about 15 kDa and about 20 kDa.
 4. The polypeptide fragment according to claim 1, wherein said fragment is a carboxy terminal fragment of said human IL-1β precursor polypeptide.
 5. A purified human IL-1β polypeptide fragment, with the proviso that said polypeptide fragment is not the mature form of human IL-1β, produced by the process of expressing in a cell a recombinant polynucleotide wherein said recombinant polynucleotide comprises a polynucleotide sequence that encodes said human IL-1β polypeptide fragment, wherein said process further comprises purifying said human IL-1β polypeptide fragment using antibodies that specifically bind to said human IL-1β polypeptide fragment; and wherein said human IL-1β polypeptide fragment has IL-1β biological activity as determined in a mouse thymocyte assay. 